This invention relates generally to portable apparatus for freezing the liquid contents of pipes for working on the pipe, and to the more particular field of portable pipe freezers that use a refrigerant cycle for cooling the pipe.
Pipe freezers are used in repairing or replacing pipe sections or repairing or adding fittings. When there is no convenient shut-off valve, the effect of blocking flow in the pipe can be achieved by freezing the water in a section of the pipe. The frozen section acts as an ice plug that blocks flow.
Some pipe freezer devices use frozen CO2 (dry ice) for the heat transfer to freeze the section of pipe. This invention however, relates to devices that use a refrigerant in a refrigeration cycle for the heat transfer. Such devices are described, for example, in U.S. Pat. No. 5,548,965 and its counterparts DE 196 17 619.0 and GB 2,301,661. The same patent describes an evaporator head with multiple channels sized to fit various standard pipe diameters. Two evaporator heads are connected to a portable condenser/compressor unit by flexible coaxial tubes that cycle refrigerant to and from the evaporation chambers.
This invention improves upon the pipe freezer of U.S. Pat. No. 5,548,965 by structural differences that make it easier to install the evaporator heads in some situations; specifically the use of interchangeable adapters that slide onto the evaporator chambers to adapt the head for pipes of different diameters. The invention further adds internal structural differences that improve the distribution and flow path of the refrigerant along the pipe section, and thus improve the evaporation heat exchange.
The invention is in an apparatus for freezing the contents of a pipe through the use of a refrigeration cycle. The apparatus includes a portable condenser/compressor unit and a pair of flexible coaxial hoses connected to an evaporation chamber. A set of interchangeable adapters, each configured with one or more nearly semicircular channels conforming to a standard pipe diameter are used to place the evaporation chamber along and in heat transfer conduction with a section of a pipe. The adapters are configured to hold the evaporation chamber in a position such that the length axis of the chamber is aligned parallel to the axis of the pipe. The evaporation chamber has its coupling for the refrigerant hose located along its length dimension. The coupling orients the hose such that the hose is generally perpendicular to the length axis of the evaporation chamber. This angle of connection into the adapter makes it easier to install the evaporator head to a pipe when the pipe is close to a wall or structure that interferes with the hose being aligned parallel to the pipe.
Inside the evaporation chamber, a baffle may be placed between the outlet of the inner tube of the hose and the return to the outer tube. The baffle forces refrigerant sprayed out of the inner tube to migrate from essentially the entry point of the chamber to an end wall and then back toward the entry point before entering the outer tube. This long migration path allows more efficient evaporation in the chamber and thus more efficient heat exchange.
In a preferred embodiment, the evaporation chamber is in the shape of a right cylinder closed by a pair of end plates. A set of interchangeable adapters has on each adapter a channel of greater than semicircular arc and a radius just slightly larger than that of the cylindrical chamber to provide a conformal xe2x80x9cslide-onxe2x80x9d fit over the cylindrical chamber. The channel defines an open slot that allows the adapter to slide past the hose coupling. The slot does not need to run the entire length of the channel, but should at least extend past the hose coupling. The channel is less than 360xc2x0 and is preferably has a less than about 330xc2x0 arc so that the slot is large enough to allow some rotational movement of the chamber within the adapter channel to facilitate connection to the pipe.
The evaporation chamber is constructed of a heat conductive metal, preferably aluminum. In a preferred embodiment, the evaporation chamber is protected from dents and scratches by installing over it a replaceable open cylindrical sleeve. When the sleeve is used, the adapters are sized to provide a slide-on conformal fit over the sleeve.